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  Direction determination utilizing vehicle yaw rate and change in steering positionUSPTO Application #: 20070118263Title: Direction determination utilizing vehicle yaw rate and change in steering position Abstract: A direction determination system particularly useful with a retrofit automatic steering system compares the rate of change of vehicle yaw rate and the rate of change of the steering wheel position. A determination of the direction is made by comparing the sign of the steering wheel angle change and the sign of the yaw rate change. The GPS course can be monitored after the direction has been determined to provide a more rapid response to changing direction. A change in direction is indicated when the vehicle speed transitions to zero and the GPS course generally reverses. Even when the direction is known, the steering wheel angle and yaw rate changes can be monitored to verify that the direction indication is correct. (end of abstract) Agent: Deere & Company - Moline, IL, US Inventor: Frederick William Nelson USPTO Applicaton #: 20070118263 - Class: 701041000 (USPTO) Related Patent Categories: Data Processing: Vehicles, Navigation, And Relative Location, Vehicle Control, Guidance, Operation, Or Indication, Vehicle Subsystem Or Accessory Control, Steering Control The Patent Description & Claims data below is from USPTO Patent Application 20070118263. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to automatic steering systems and, more specifically, to determine operational direction of a vehicle from vehicle yaw rate and steering wheel movement. BACKGROUND OF THE INVENTION [0002] In order to work properly, an automatic steering system for a vehicle must recognize if the vehicle is operating in a forward mode or a reverse mode. To turn the vehicle a given direction, movement of the steering device during operation of the vehicle in a forward mode typically is the opposite of the movement of the device during operation of the vehicle in reverse. Many presently available integrated automatic steering or tracking systems can determine the vehicle gear selected and the direction of travel. However, some non-integrated steering systems lack a transducer or other attachment that can readily communicate the actual vehicle operational direction to the controller. An example of a non-integrated system is a retrofittable steering control with a drive mechanism that attaches to a steering column or contacts an existing steering wheel for automatic steering control such as described in my commonly assigned U.S. patent application Ser. No. 11/019,482 entitled Automatic Steering Control, filed 21 Dec. 2004. Even in systems wherein the selected gear and direction is readily determinable, further verification of the direction is often desired. SUMMARY OF THE INVENTION [0003] It is therefore an object of the present invention to provide an improved system and method for determining vehicle direction. It is a further object to provide such a system and method which overcomes most or all of the aforementioned problems. [0004] It is another object to provide an improved system and method for determining vehicle direction which can operate independently of gear select switches and which is particularly useful with retrofittable steering controls. [0005] A system constructed in accordance with the present invention compares the rate of change of the yaw rate and the rate of change of the steering wheel or steering control position. If the steering wheel is turned to the right and the vehicle is in a forward gear, then the vehicle yaw rate will go to the right. If the steering wheel is turned to the right and the vehicle is in reverse gear, the vehicle yaw rate will go to the left. Upon vehicle start up, the direction is set to unknown. Once vehicle speed, steering wheel turn and vehicle yaw reach preselected thresholds, a determination of the vehicle direction can be made by comparing the sign of the steering wheel angle change and the sign of the yaw rate change. If the signs match, then the vehicle is in a forward gear. If the signs do not match, then the vehicle is in reverse. [0006] As a further enhancement to this method, the GPS course can be monitored after the direction has been determined to provide a more rapid response to changing direction. A change in direction is indicated when the vehicle speed transitions to zero and GPS course change approaches 180 degrees. Even when the direction is known, the steering wheel angle and yaw rate changes can be monitored to verify that the direction is correct. [0007] The system provides a direction indication without need for an input from the vehicle transmission or shift control. Therefore, a direction determination input for an automatic steering system, even a system which is retrofitted to an existing vehicle is easily attainable. [0008] These and other objects, features and advantages of the present invention will become apparent from the description which follows taken with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIG. 1 is a schematic representation of steering structure for converting-a manual steering system to an automatic system, the system including direction determination structure. [0010] FIG. 2 is an exploded view of a portion of the steering structure of FIG. 1. [0011] FIG. 3 is a flow chart illustrating a method for determining vehicle direction. [0012] FIG. 4 is a flow chart illustrating a method for continually monitoring the vehicle direction once an initial direction determination has been made. DESCRIPTION OF THE PREFERRED EMBODIMENT [0013] Referring now to FIG. 1, therein is shown an off-road vehicle 10 such as a tractor or utility vehicle having an operator station 12 supported for movement over the ground by steerable wheels 14. The wheels 14 are connected to a conventional steering mechanism or control 16 which includes a rotatable steering shaft 20 supported within a steering column 22 which projects upwardly at the operator station 12. A steering wheel 30 with a hand grip portion 31 is supported at the upper end of the shaft 20 for manual steering operation by the operator. [0014] As shown, the steering wheel 30 is part of conversion structure indicated generally at 32 for providing an automatic steering function on a vehicle normally equipped with manual steering only. Alternatively, the original steering wheel of the vehicle may be mounted on the conversion structure 32. The conversion structure is fully described in my aforementioned co-pending application U.S. patent application Ser. No. 11/019,482 entitled Automatic Steering Control. [0015] Pulley structure 34 is connected for rotation with the shaft 20 about the shaft axis at a location adjacent the connection of the steering wheel 30 with the shaft 20. A motor 40 is supported from the column 22. Pulley structure 44 drivingly connects the motor 40 to the pulley structure 34. As shown, the pulley structures 34 and 44 are pulleys connected by a chain, conventional drive belt or timing belt arrangement 46. However, other types of drives such as gear drives may also be used. For example, a motor may be mounted on the end of the steering shaft 20 to provide direct drive to the shaft 20 at a location offset from hand grip portion 31. [0016] A processor 50 is located on the vehicle 10 and includes a control output 52 connected through a CAN harness 54 to an input 56 of the motor 40. A position feedback output 58 on the motor 40 is connected to an input of the processor 50. As shown, the motor 40 is an electric stepper motor, and the feedback device is an encoder located on the motor 40 and providing signal over a feedback line 58 indicative of the number of steps the motor 40 has moved. The motor 40 remains drivingly connected to the steering shaft 20 in both a manual steering mode and an automatic steering mode so that the encoder is capable of providing a shaft position signal to the processor 50 in both modes. [0017] The processor 50 is connected to position sensor structure indicated generally at 60 in FIG. 1, such as a conventional global positioning system (GPS) with a receiver 61 that receives signals 62 from one or more remote locations. Additional correction inputs such as a RTK ground based differential correction input may be provided from an RTK radio 63, and a terrain compensation input may be provided from a terrain compensation module (TCM) 65. The TCM 65 corrects GPS data for roll angle and yaw as the vehicle 10 moves over uneven terrain and provides a yaw rate signal utilized in the direction determination feature discussed in detail below. [0018] The system 60 is connected through CAN 54 to an input of the processor 50. A steering system unit (SSU) 70 is connected through a CAN harness 71 and a system connector 72 to the CAN harness 54 and to a system display 73. The SSU 70 receives control information from the processor 50 and position feedback information via line 58 from the encoder on the motor 50. An on-off and resume switch 78 is connected to the SSU 70. [0019] The processor 50 determines the position of the vehicle and compares the position to a desired position and intended path of the vehicle. An error signal is generated, and the motor 40 is activated to move a preselected number of steps depending on the error signal. Detection devices, such as a ground speed detector and lateral velocity, provide signals utilized by the processor 50 to increase the accuracy of the automatic steering system. Continue reading... Full patent description for Direction determination utilizing vehicle yaw rate and change in steering position Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Direction determination utilizing vehicle yaw rate and change in steering position patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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